In a motor vehicle, multiple electronic control units (ECUs) are installed and interconnected. For the connections, point-to-point connections or bus connections may be used. The electronic control units exchange messages among one another to jointly provide an improved function. For example, two electronic control units may be provided in the form of an anti-lock braking system and a navigation system, the speed of the motor vehicle being determined by the anti-lock braking system and subsequently made available to the navigation system in order to make it possible for the latter to have an improved destination guidance on a predetermined route.
If there is an error in one of the electronic control units, the other electronic control units may thus also be limited in their operation. In this case, more problems often ensue if the first electronic control unit makes available erroneous information than if the information fails to appear entirely. If the first electronic control unit determines an error in its own function which cannot be remedied, it may put itself into a safe operating mode in which it fulfills the functions assigned to it at least partially. In the case of an engine control unit, an emergency operation may be possible in this way at a low vehicle speed, for example.
The other electronic control units may respond to that by also putting themselves into safe operating modes in which they each fulfill their tasks at a lower failure risk, but only partially, if necessary. For this purpose, a data bus which interconnects the electronic control units may be subdivided into subnetworks, thus allowing electronic control units which are not fully functional to be disconnected from the others.
This mode of operation is, however, limited to errors which occur during ongoing operation of the motor vehicle and may be recognized by the electronic control units themselves or mutually. An object of the present invention is to provide a method and a device for proactively remedying a malfunction of an electronic control unit on board a motor vehicle.